Fuel injection systems of this type are used in modern petrol or diesel engines. In addition to the injectors, the high pressure rail, said injectors also have a high pressure fuel pump for generating the necessary pressure. In this context, fuel is fed from a fuel tank by a pre-feed pump to the high pressure pump which feeds the fuel under high pressure to the high pressure rail. The injectors are fed via the high pressure rail.
In modern injection systems, high pressure fuel pumps with digital inlet valves are used. The term digital inlet valve here denotes a valve which assumes only an open position or closed position and is not actuated to assume intermediate positions. Such digital inlet valves are activated electromagnetically. In the inlet phase, the inlet valve is opened, with the result that the piston of the high pressure pump can suck fuel into the cylinder. In the feed phase, the inlet valve is closed and the piston of the high pressure pump forces fuel into the high pressure system.
In other embodiments (valves which are closed in the currentless state (D/V), the inlet valve is kept open electrically during the induction and is deactivated in the expulsion phase if feed is desired.
Electrical energy is required to activate such a digital inlet valve. Furthermore, switching noise is generated owing to the opening/closing of the digital inlet valve. Such noise emissions are undesired. There is also generally an interest in lowering the energy consumption of such injection systems.
Certain methods are known for reducing the noise emissions owing to the actuation and therefore the closing and/opening of a digital inlet valve. An example of this is to use a specific current profile to actuate the digital inlet valve. This method is relatively costly.